Natural Selection: Hardy-Weinberg
Natural Selection: Hardy-Weinberg
Refer to the instructions that accompany this worksheet.
Materials List
- 50 red beans
- 50 white beans
- 1 paper bag or deep bowl
- 3 dishes or containers
In this activity, we will address the following question: How does natural selection affect gene frequency over several generations?
Read the instructions for the Natural Selection lab.
Hypothesis section
Specifically, what research question will this experiment test?
Hypothesize about how the frequency of the two alleles (F and f) will change over time. Explain why you expect these results.
Follow the steps for the procedure in the instructions. Record your data the data table on the following page.
Data Table
| Generation | Number of FF individuals | Number of Ff Individuals | Number of ff Individuals | Number of F alleles | Number of f alleles | Total Number of alleles | Gene Frequency of F | Gene Frequency of f |
| 1 | ||||||||
| 2 | ||||||||
| 3 | ||||||||
| 4 | ||||||||
| 5 | ||||||||
| 6 | ||||||||
| 7 | ||||||||
| 8 | ||||||||
| 9 | ||||||||
| 10 |
On the following page, insert the graph you created in Excel that shows your results.
Graph
Paste graph here
Questions:
1. Do your results support or reject your hypothesis? Explain.
2. Compare the frequencies of the dominant allele to the frequencies of the recessive allele.
3. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How might emigration and immigration affect the gene frequency of F and f in this population of rabbits? How might you simulate this effect if you were to repeat this activity?
4. How does natural selection affect gene frequency over several generations?
5. How are the results of this simulation an example of evolution?
PLACE THIS ORDER OR A SIMILAR ORDER WITH SMASHING ESSAYS
Natural Selection Lab: Hardy-Weinberg
In this activity, you will examine natural selection in a small population of wild rabbits.
Evolution, on a genetic level, is a change in the frequency of alleles in a population over a period of time. Breeders of rabbits have long been familiar with a variety of genetic traits that affect the survivability of rabbits in the wild, as well as in breeding populations. One such trait is the trait for furless rabbits (naked bunnies). This trait was first discovered in England by W.E.
Castle in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a definite selective force against it.
Note: In this lab, the dominant allele for normal fur is represented by F and the recessive allele for no fur is represented by f. Bunnies that inherit two F alleles (homozygous dominant) or one F and one f allele (heterozygous) have fur, while bunnies that inherit two fs (homozygous recessive) have no fur.
Procedures
- Download and open the accompanying lab worksheet. Answer the first two questions on the first page (the hypothesis section) before completing the experiment.
- The red beans represent the allele for fur (F), and the white beans represent the allele for no fur (f). The container represents the English countryside, where the rabbits randomly mate.
- Label one dish FF for the homozygous dominant genotype. Label a second dish Ff for the heterozygous genotype. Label the third dish ff for those rabbits with the homozygous recessive genotype.
- Place the 50 red and 50 white beans (alleles) in the container and shake up (mate) the rabbits. (Please note that these frequencies have been chosen arbitrarily for this activity.)
- Without looking at the beans, select two at a time, and record the results on the da ta form next to “Generation 1.” For instance, if you draw one red and one white bean, place a mark in the chart under “Number of Ff individuals.” Continue drawing pairs of beans and recording the results in your chart until all beans have been selected and sorted. Place the “rabbits” into the appropriate dish: FF, Ff, or ff. (Please note that the total number of individuals will be half the total number of beans because each rabbit requires two alleles.)
- The ff bunnies are born furless. The cold weather kills them before they reach reproductive age, so they can’t pass on their genes. Place the beans from the ff container aside before beginning the next round.
- Count the F and f alleles (beans) that were placed in each of the “furred rabbit” dishes in the first round and record the number in the chart in the columns labeled “Number of F Alleles”
and “Number of f Alleles.” (This time you are really counting each bean, but don’t count the alleles of the ff bunnies because they did not survive to reproduce.) Total the number of F alleles and f alleles for the first generation and record this number in the column labeled “Total Number of Alleles.” - Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age) back into the container and mate them again to get the next generation.
- Repeat steps five through eight to obtain generations two through ten.
- Determine the gene frequency of F and f for each generation and record them in the chart in the columns labeled “Gene Frequency of F” and “Gene Frequency of f.” To find the gene frequency of F, divide the number of F by the total, and to find the gene frequency of f, divide the number of f by the total. Express results in decimal form. The sum of the frequency of F and f should equal one for each generation.
- Graph your frequencies. Prepare a graph with the horizontal axis as the generation and the vertical axis as the frequency in decimals. Plot all frequencies on one graph. Use a solid line for F and a dashed line for f.
- Answer the remaining questions on the worksheet.
PLACE THIS ORDER OR A SIMILAR ORDER WITH SMASHING ESSAYS
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